1. Field of the Invention
The present invention relates to variable optical-property elements such as a variable focal-length lens, a variable focal-length diffraction optical element, a variable deflection-angle prism, and a deformable mirror, and to an optical apparatus such as spectacles, a video projector, a digital camera, a TV camera, an endoscope, a telescope, or a camera finder, having an optical system including such variable optical-property elements.
2. Description of Related Art
Conventional lenses have been manufactured by polishing glass. Since the lens itself cannot vary a focal length, a mechanical structure is complicated because a lens unit must be moved along the optical axis for focusing or zooming of a camera, or changing magnification.
Because a motor or the like is used for moving a part of the lens unit, this conventional practice has disadvantages that power consumption is large, noise is produced, response time is long, and much time is required for moving lenses.
For shake prevention as well, mechanical movement of the lenses by a motor or a solenoid causes defects such as a large power consumption and a complicate mechanical structure, resulting in a higher cost.
In a zoom imaging optical system such as a digital camera, the problem is raised that the position of an image on an imaging plane is considerably shifted, depending upon the focal position of reflected light, resulting in a change in a field direction.
Use of a prism of high refractive index causes inconvenience that aberration cannot be completely corrected.
It is, therefore, an object of the present invention to provide an optical system comprising a variable optical-property element such as a variable focal-length lens, a deformable mirror, or a variable deflection-angle prism, which is low in power consumption, quiet, and short in response time to contribute to cost curtailment, and small in variation of the image position on the imaging plane, and permits sufficient correction for aberration caused by a shape error, and an optical apparatus including the optical system.
In order to achieve the above object, the optical apparatus according to the present invention is provided with a deformable mirror which has positioning marks within or outside a beam passing range of the deformable mirror and on frames for mounting the deformable mirror.
The optical system according to the present invention is provided with a deformable mirror in which, in order to reduce variation of the image position on the imaging plane in at least two states with different shapes of the deformable mirror, first and lower-order terms in an equation expressing the surface of the deformable mirror are changed in the above-mentioned two states.
The optical system according to the present invention is provided with an optical element having a rotationally asymmetric optical surface in order to correct aberration produced by a shape error of the deformable mirror.
This and other objects as well as the features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.